In a chromatograph (a liquid chromatograph and a gas chromatograph), if an external condition independent of the characteristics of the sample (such as the pressure of a mobile phase, the room temperature or the temperature in a column oven) changes due to some reasons during an analysis, it is impossible to correctly obtain data, such as the retention time. Therefore, in an analysis using a chromatograph, those external conditions are continuously monitored, and when a measured value is found to have deviated from a normal range, a measure is taken to prevent the analysis from being continued under abnormal conditions. Examples of the measure to be taken include alarming users by sound or light, automatically discontinuing the analysis and/or restarting the analysis after automatically resolving the abnormality (for example, see Patent Literature 1).
In recent years, new standards (guidelines) called GLP (Good Laboratory Practice) and GMP (Good Manufacturing Practice) have been introduced in some fields, such as the inspection of foodstuffs as well as the development and evaluation of new medicines, in order to ensure the reliability of the measurement results. GLP/GMP impose severe standards on the management of data which include the set conditions used in a test or inspection as well as its result, and the validity of the analyzing system used in the measurement needs to be verified. In the case of an analysis using a chromatograph, those requirements cannot be satisfied by merely preventing an analysis from being performed under abnormal conditions; it is also necessary to keep a log which proves that the analysis has been normally performed. To this end, in conventional chromatographs, the measured data of the aforementioned external conditions are saved and linked with the data obtained from a sample in each analysis as well as other items of information.
The data of the external conditions thus saved are not only available for proving that the analysis has been normally performed; those data can also be used to analyze their temporal change and prevent abnormalities from actually occurring. For example, the pressure of the mobile phase changes with the aging of the column, and therefore, the obtained pressure data shows a temporal change in which the pressure gradually changes within a normal range toward abnormal values. From this temporal change, it is possible to estimate the timing to replace the column.